I don't know the exact equation, but accelerating any mass beyond that of a single particle or perhaps molecule to that large a fraction of the speed of light b

I don't know the exact equation, but accelerating any mass beyond that of a single particle or perhaps molecule to that large a fraction of the speed of light borders on impossible. The energy required to accelerate a mass increases exponentially, so getting any appreciable mass to .999c is pretty much out of the question. Again, no equation (if someone has it I'd love to plug in some numbers) but I'm guessing it would require on the order of the total energy output of the sun to get even a modest spacecraft to that velocity. "The Physics of Star Trek" by Lawrence Krauss had the equation I believe, but I can't find it!